1. Field of the Invention
The present invention relates to a semiconductor light emitting element and a light emitting device using the same, and particularly, to an electrode structure of the light emitting element.
2. Description of the Related Art
A variety of researches have been made on the light emitting element using a nitride semiconductor, since light emission is obtained in the near-ultraviolet area to the red color area due to a wide band gap property of the light emitting element. A typical basic structure of the nitride semiconductor light emitting element is a structure where an n-type nitride semiconductor, an active layer and a p-type nitride semiconductor are laminated on a substrate, and respective electrodes are provided in the p-type layer and the partially exposed n-type layer. The structure of the light emitting element including the electrode structure has been under study. Especially in an effort to make the element high-powered, a variety of light emitting element structures and electrode structures have been proposed.
Patent 1: Japanese Patent Laid-Open Publication No. 2003-045898
Patent 2: Japanese Patent Laid-Open Publication No. 2005-229085
Patent 3: Japanese Patent Laid-Open Publication No. 2003-133590
Patent 4: Japanese Patent Laid-Open Publication No. 2004-179347
Patent 5: Japanese Patent Laid-Open Publication No. 2005-317931
Patent 6: Japanese Patent Laid-Open Publication No. 2001-102631
Patent 7: Japanese Patent Laid-Open Publication No. 2004-128321
Patent 8: Japanese Patent Laid-Open Publication No. 2002-016282
Patent 9: Japanese Patent Laid-Open Publication No. 2002-221529
Patent 10: Japanese Patent Laid-Open Publication No. H9-232632 (Paragraph Nos. 51-63, FIGS. 7-9)
Proposals that have conventionally been made relate to a structure where a transparent electrode such as ITO (indium tin oxide) is used for an n-electrode provided in the n-type layer (the Patents 1 and 2), and a structure as a double-layer structure where a metal layer/reflection layer is superposed in part (the Patents 3 and 10) or all (the Patents 4 and 5) of the upper layer.
Other proposals include: lowering the n-electrode with respect to light emission from the active layer to suppress a light shielding effect (the Patent 6); and tilting the side face of the n-electrode to enhance a reflection effect (the Patent 7). Further, providing a concavo-convex structure inside the light emitting structure to enhance light extraction efficiency has also been proposed (the Patents 8 and 9).